Along with rapid development of the wireless communications technology, a requirement from a mobile user on capacity and quality of wireless communications becomes higher and higher, and thus an MIMO technique, namely an MIMO wireless communications technique is proposed. In the MIMO wireless communications technique, a multi-antenna unit is adopted by an MIMO wireless communication system both at a sending end and a receiving end. Therefore, a design of the MIMO antenna becomes an important part in the MIMO wireless communications system.
In the design of the MIMO antenna, in order to obtain a good MIMO performance, not only each antenna unit is needed to have a good performance, but also a good anti-interference performance between two antenna units is needed. Generally, an electromagnetic coupling effect between two adjacent antenna units may distort current distribution on an antenna, and distortion of the current distribution may not only change radiation pattern of the antenna unit, but also change an impedance of the antenna. The nearer a distance between two antenna units is, the stronger electromagnetic coupling between the two antenna units is; the lower isolation is, the lower radiation efficiency of the antenna is.
However, currently the size of a mobile terminal device becomes smaller and smaller, it is urgent to solve a problem regarding how to provide high isolation to the MIMO antenna in the mobile terminal device which becomes smaller and smaller